The present invention relates to a driver circuit, an electro-optical device, an electronic instrument, and the like.
As a liquid crystal display (LCD) panel (display panel in a broad sense; electro-optical device in a broader sense) used for electronic instruments such as portable telephones, a simple matrix type LCD panel and an active matrix type LCD panel using a switching element such as a thin film transistor (hereinafter abbreviated as “TFT”) have been known.
The simple matrix method can easily reduce power consumption as compared with the active matrix method. On the other hand, it is difficult to increase the number of colors or display a video image using the simple matrix method. The active matrix method is suitable for increasing the number of colors or displaying a video image, but has difficulty in reducing power consumption.
The simple matrix type LCD panel and the active matrix type LCD panel are driven so that the polarity of the voltage applied to a liquid crystal (electro-optical substance in a broad sense) forming a pixel is reversed alternately. As such an alternating drive method, line inversion drive and field inversion drive (frame inversion drive) have been known. In line inversion drive, the polarity of the voltage applied to the liquid crystal is reversed in units of one or more scan lines. In field inversion drive, the polarity of the voltage applied to the liquid crystal is reversed in field (frame) units.
In this case, the voltage level applied to a pixel electrode forming a pixel can be reduced by changing a common electrode voltage (common voltage) supplied to a common electrode provided opposite to the pixel electrode in synchronization with the inversion drive timing.
When using such alternating drive, power consumption increases accompanying charging or discharging the liquid crystal. In order to solve this problem, JP-A-2002-244622 discloses technology of reducing power consumption by initializing a charge stored in a liquid crystal to zero by short-circuiting two electrodes provided on either side of the liquid crystal during inversion drive, thereby causing the voltage to transition to the intermediate voltage before short-circuiting the electrodes, for example. JP-A-2004-354758 discloses technology of reducing power consumption by applying a precharge potential to the source line in a first precharge period before a pixel electrode write period and a second precharge period before changing the common electrode voltage, thereby reducing a change in potential of the source line when changing the common electrode voltage.
However, the technologies disclosed in JP-A-2002-244622 and JP-A-2004-354758 have a problem in that the effect of reducing power consumption varies depending on the voltage applied to the source line. Therefore, the effect of reducing the amount of charge by charging or discharging the common electrode, of which the polarity of the applied voltage is reversed, may be insufficient. According to the technology disclosed in JP-A-2002-244622, the amount of charging/discharging may be increased by short-circuiting the two electrodes provided on either side of the liquid crystal depending on the relationship between the voltage applied to the source line and the polarity of the common electrode voltage, whereby the effect of reducing power consumption may be reduced. Therefore, when recycling the supplied charge, it is preferable that the source line and the common electrode be driven while reliably reducing power consumption using a simple configuration.
On the other hand, priority may be given to a reduction in chip size and mounting area of a driver circuit and the like at the expense of the effect of reducing power consumption to some extent, depending on the application field of the driver circuit. This applies to the case of applying the driver circuit and the like to a product for which the customer (electronic instrument manufacturer) gives the highest priority to a reduction in cost of the driver circuit or an LCD panel including the driver circuit, for example.
Therefore, it is desirable to provide a driver circuit and the like which make it possible to give priority to a reduction in power consumption or a reduction in cost depending on the customer. Specifically, it is desirable that power consumption be minimized at the expense of a cost reduction effect to some extent (priority is given to reduction in power consumption) or cost be minimized at the expense of a power consumption reduction effect to some extent (priority is given to reduction in cost) using a simple configuration. It becomes possible to satisfy various users' demands using one type of driver circuit by providing such a driver circuit and the like, whereby the manufacturing cost can be further reduced.
According to the technology disclosed in JP-A-2-244622, since the potentials are adjusted by recycling a charge by means of a short circuit, a means which drives a load is not provided. Therefore, it takes time to recycle a charge. As a result, when the pixel electrode write time within one horizontal scan period is reduced, a charge recycle time may become insufficient. The pixel electrode write speed may be increased by the precharge technology disclosed in JP-A-2004-354758, for example. However, JP-A-2004-354758 does not disclose the configuration of a driver circuit and the like which make it possible to give priority to a reduction in power consumption or a reduction in cost depending on the customer.